The field of the invention is that of thermostats, more specifically service thermostats.
Thermostats are well known in the art. They operate to command a temperature control or conditioning system. During normal operation, thermostats function to maintain a desired ambient temperature. Based on the commands given by the thermostat, the temperature control system provides the specified desired ambient temperature.
Service thermostats operate similarly. Like conventional normal control thermostats, the service thermostat issues commands to the temperature control system. However, the service thermostat does not necessarily issue commands on the basis of a specified desired temperature. Rather, it issues commands according to the diagnostic efforts of a service technician.
One important distinction between the two types of thermostats involves the location of the thermostat user. For a control thermostat, a home owner sets the desired temperature in living areas, which are typically far from the system elements to be diagnosed. Service technicians monitor certain predefined temperature control operations where the machinery is located, normally outside the house, in garages or basements. Thus, a service person desires to operate the service thermostat relatively near the machinery being serviced. Having the flexibility of a service thermostat facilitates rendering service.
U.S. Pat. No. 4,146,085 (Wills) describes a service thermostat device. The system described in Wills has single lights which indicate the activity or inactivity of various heat pump components. Additionally, the Wills device has an ohm meter which checks the various sensors and also provides an indication of the temperature at various points in the system. The Wills device is used as a diagnostic tool which is dedicated to servicing. Further, the diagnostic thermostat described in Wills must be attached to the logic module (the temperature control system master controller). In effect, the Wills device replaces the sensor inputs to the logic module with its own inputs. Thus, when utilizing the Wills device, no temperature sensors are attached to the system.
Also, the diagnostic thermostat in Wills is designed for use in a single speed heat pump. Compared to a service thermostat needed for a single speed heat pump, variable speed equipment requires a much greater degree of complexity. A general computer could accomplish the service thermostat tasks, but this would entail a much greater expense than the usual service thermostat.
What is needed in the art is a service thermostat for a variable speed temperature control system. Additionally, what is needed in the art is a service thermostat which connects anywhere in the temperature control system. Further, a service thermostat is needed which can serve as a normal thermostat.